The present invention relates to a method and apparatus for inserting and retrieving wear bushings of various diameters in a well head casing.
A wear bushing is provided for a well head casing during drilling operations to protect an upper end of the casing from engagement with the drill bit as the drill bit is lowered or raised through the casing. The wear bushing also prevents contact between the drill pipe sections and the well head casing as the drill pipe sections are rotated during normal rotary drilling operations. By providing the wear bushing, a smooth surface is retained within the well head casing to inhibit leaks from appearing in the casing upon completion of the drilling operations.
The wear bushing, however, must be conveniently able to be removed from the casing for various reasons. For example, the wear bushing may become worn from the action of the continuously rotating drill pipe sections against the wear bushing. Further it is desirable to withdraw the wear bushing to conduct tests to determine whether or not any portion of the casing has been demaged or contains leaks. In addition, it is required by the U.S.G.A. that a test plug be inserted in the well head casing once a week during drilling to test for blowout prevention. In order to insert the test plug in the well head casing, it is necessary to remove the wear bushing.
Various wear bushing retrieving tools have been proposed whose configuration is dependent upon the particular type of wear bushing to be retrieved. One such tool, for use with a wear bushing of the type having vertical access slots on an upper inner peripheral surface of the wear bushing which slots communicate with a retrieving groove arranged around the inner peripheral surface of the wear bushing, consists of a cylindrical member with a number of studs (corresponding to the number of access slots) welded to an outer surface of the cylindrical member. A tool of this type, however, has the disadvantage that it is only useful with a wear bushing of a single diameter. Also, a device of this type has the further disadvantage that if one of the studs breaks off during operation the retrieving tool cannot be easily repaired at the drilling site.
Another known retrieving tool is disclosed in U.S. Pat. No. 3,645,328 issued Feb. 29, 1972 to Greene, Jr. The Greene, Jr. patent relates to a retrieving apparatus comprising a plurality of legs which are held in an inward position by a flange. Upon releasing the flange, the arms move outwardly to engage a lower edge of a wear bushing. An apparatus of the type disclosed in the Greene, Jr. patent is not adaptable for use with a large number of wear bushings having different diameters. Also, a device of this type cannot be repaired easily if one of the legs breaks during a retrieving operation.
U.S. Pat. No. 3,489,214 issued Jan. 13, 1970 to Phipps et al discloses a wear bushing retrieving tool which includes a plurality of fixed pins which engage and withdraw a wear bushing. The tool in the Phipps et al patent comprises a sleeve which is placed over a drill pipe section and held in place by a pair of screws. A tool of this type, however, cannot be adapted to retrieve wear bushings of various diameters.
U.S. Pat. No. 3,473,608 issued Oct. 21, 1969 to Castille discloses a retrieving tool having a plurality of spring biased arms which engage an upturned groove provided on an inner wall of a wear bushing. The outward movement of the arms is limited by a stop which also provides additional support for the arms as the wear bushing is lifted from a well head casing. There is no disclosure in the Castille patent of providing a plurality of adjustable members which allow the effective diameter of a retrieving tool to be varied to retrieve wear bushings of various diameters. Also, a device of the type disclosed in the Castille patent is complex and is difficult to repair at the drilling site in the event of breakage of the tool.
Accordingly, it is an object of the present invention to provide a wear bushing retrieving method and apparatus which is simple in construction and operation yet is adaptable to retrieve wear bushings having a large range of different diameters.
A further object of the present invention is to provide a retrieving tool which can be easily adjusted or repaired in case of breakage at the site of the drilling.
It is still a further object of the present invention to provide a retrieving tool which is useful with wear bushings of several different configurations. Another object of the present invention is to provide a retrieving tool which is adjustable to retrieve wear bushings having various diameters and configurations without requiring the use of any special tools or knowledge.
A further object of the present invention is to provide a method for adapting a single retrieving tool for retrieving wear bushings having various different inside diameters.
These and other objects of the present invention are accomplished by a wear bushing retrieving tool comprising an elongated member having first and second ends. The elongated member includes a generally cylindrical outer peripheral portion arranged parallel to a longitudinal axis of the elongated member. A plurality of adjustable members adapted for engaging a wear bushing are arranged at the cylindrical outer peripheral portion of the elongated member. Each of the adjustable members extends outwardly from the cylindrical portion an adjustable distance generally along a radius of the cylindrical portion. In addition, the plurality of adjustable members is selectively variable in quantity.
In a preferred embodiment, each of the adjustable members comprises a bolt which is screwed into a respective tapped hole in the cylindrical outer peripheral portion. Each of the bolts can be easily adjusted to any effective diameter which is determined by the diameter of the wear bushing to be retrieved. It is also preferred to provide a plurality of washers which maintain a head of each of the bolts at a desired outward distance from the cylindrical portion. The retrieving tool of the present invention also includes a plurality of tapped holes in the cylindrical portion of the elongated member such that the retrieving tool of the present invention can be adapted for use in retrieving wear bushings having various numbers of access solts communicating with a retrieving groove on an inside surface of the wear bushing.
A further preferred embodiment of the present invention includes an annular ring which has an opening in the center thereof which opening is adapted to slide over the elongated member of the retrieving tool. The annular ring is secured intermediate the ends of the elongated member and includes a generally cylindrical outer peripheral surface which has a diameter which is larger then the diameter of the cylindrical outer peripheral portion of the elongated member. A plurality of adjustable members are provided in the outer peripheral surface of the annular ring. In this way, a single retrieving tool can be adapted for use with a larger range of diameters of wear bushings.
A method for adapting a single wear bushing retrieving tool for retrieving wear bushings of various different inside diameters according to the present invention comprises selecting a quantity of adjustable members to correspond with a number of access slots in a wear bushing to be retrieved. An end of each of the selected quantity of adjustable members is inserted in an appropriate bore in a first cylindrical outer peripheral surface of the single retrieving tool. Each of the selected quantity of adjustable members is adjusted within the openings such that the effective diameter of the adjustable members is slightly less than an inside diameter of a retrieving groove in the wear bushing.